Spark-plug



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ALBERT J'. CHAMPIDN, 0F FLINT, MICHIGAN, ASSIG'NR' TO CHAMPION IGIN'IIION` COMPANY, F FLNT, MICHXGAN, A CORPORATION 0F MICHIGAN.

. eraan-PLU@ assenti.

specification of Letters raient.

Patented May 4:, 1920.

Application filed November 3G, i917. Serial No. 204,568.

new' and useful Improvements in Spark- Plugs, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates to spark-pl ugs more particularly designed for usein connection l with high-speed internal combustion engines and has foi` its object the protection of the electrodes and insulator and avoidance of pre-ignition.

In the drawing, my improved shown in sectional elevation.

`A is the casing of the plug having the plug is usual threaded nipple B, C is the insulator within the casing, D is the insulated electrode and E the grounded electrode. it is the primary object of the invention to protectthe insulator and the electrode. carried thereby vfrom the intenseheat. vAt the same tim it is essential to avoid short-circuiting., by lhe sooting ofthe insulator and also' to avoid retention of flame or slowly burning gas which would cause pre-ignition. Heretofore various constructions have been devised in which the insulator isV shielded from the heat, but with such constructions there is ,first, the danger of short-circuiting througn carbondeposit upon the cooler portions" of the insulator surface, and second, the danger that the space beyond the shield, will entrap combustible gas which by reason of its proximity to the cooled walls will burn slowly and therefore will cause pre-ignition of a subsequently introduced gaseous charge` y 'With the present construction these difficulties are overcome by so fashioning the insulator and the casing that the contour of the one will conform to that of the other but with suilicient sepa-ration to maintain the'insulation. The fact that the two surfaces are uniformly spaced from each other reduces the volume of this space to the minimum without any reduction in'the insulating properties. Furthermore the uniformly narrow space between the walls will prevent ignition of the gas therebetween.

the end of the insulator adjacent to the electrode the casing `is cut away so as to le'ave an annular portion F exposed to the flame. The heat of the flame is sutilcient` to burn oii any soot deposit, but the area of the surface which is thus exposed is so small that the heat communicated to the insulator may be readiliyv dissipated as well as the heat which is communicated to the electrode. As specifically shown the insulator is seated. in the casing upon a gaslretl G upon the shoulder H, and the `portion I projecting inward therefrom is of slightly tapering section and rounded at' its inner end. VThis portion is within the threaded nipple portion B of the casing, the walls of which are cooled by contact with the water jacket of the engine, and as shown the contour J of these walls is parallel to the contour of the linsulator' and Abut slightly spaced therefrom. This will form a portion K wardly to partially shield the end of the at the inner end which projects ininsulator, leaving only the small annular exposed portion F, and the inner end of the casing has the flaring mouth L within which are arranged the electrodes D and E.

In operation, when the explosive charge is compressed only a relatively small volume of the gas can 'be forced into the restricted space between the insulator and the surrounding walls of the casing. This slight 4volume of gas will be expelled during the expansion stroke, and any remnant retained in the narrow space cannot ybe ignited on account of the close proximity ofthe cooled surfaces. At the ,same time there is an extended insulating surface between the 'electrode and the point of contact of the insulator upon the casing, while the ,annular portion immediately adjacent to the electrode is cleared from any soot deposit by 'exposure to the flame.

lNhat l claim as my invention is:

in a spark plug, the combination with an insulator `and an electrode extending longitudinally therethrough, of a casing in which said insulator is seated, having a loo .threaded Iiipple portion insideof the seat I opening SurroundiIi-g said electrode, and a corresponding in'eoutour Withthe portion second electrode extending transversely'olb of said insulator inside of the seat and unithe' first-mentioned electrode and adjacent formy 'spaced therefrom a restricted disthereto, sadsecond electrode having its op- 5 .tance to prevent ignition of any gasesthereposite'ends engaging the Wall ofthe flaring between, 'said nipple portionr extending -mouth. y j f partly around the innerl end of said-ins'u- In testimony whereof I affix my signature. 1'5 later and having a Haring mouth 'With an t ALBERT J. CHAMPlON. 

